7. Correct. The answer is false. A' = T - A or all the elements not bordered by
blue, B' = T - B, or all elements not highlighted with yellow. The difference
between A' and B' = (T-A) - (T - B) = B-A gives the elements of B which do not belong
to A. So, we have that A' - B' = {Fe, Co, Ni, Zn}. The set does not include Cu.